The present invention relates to a controller for a motor including a so-called consequent pole rotor that reduces the number of magnets by half by using a magnet for only one of two different magnetic poles and using a salient pole of a core as a substitute for the other magnetic pole.
A so-called consequent pole motor (also referred to as a half magnet motor) is advantageous for saving resources and costs. The consequent pole motor includes a rotor that uses a magnet for only one of the magnetic poles to reduce the number of magnets by half. A salient pole of a rotor core is used as a substitute for the other magnetic pole (refer to, for example, Japanese Laid-Open Patent Publication No. 9-327139)
In such a consequent pole motor, the salient pole itself does not have a magnetic flux compelling force (induction). Thus, depending on the present positional relationship between the salient pole and the teeth of the opposing stator, the magnetic flux at the rear side of the magnet may not be evenly diffused from a circumferentially central part of the magnet to the salient poles at opposite sides of the magnet. Rather, the magnetic flux may be greatly induced toward the salient pole that presently has a smaller magnetic resistance. In such a case, the present magnetic flux directivity and the magnetic flux amount also change. Thus, the waveform of the magnetic flux differs between a salient pole portion and a magnet portion thereby causing the rotor to be magnetically unbalanced. When fundamental wave current (sinusoidal current) is supplied to the consequent pole motor in the same manner as a motor that uses a normal rotor having magnetic poles that all formed by magnets, this would increase torque ripple and vibration noise. It is desirable that such a state be improved.